Rare earth is a general term for a total of 17 elements including lanthanide, scandium, and yttrium. The application of rare earth elements is very extensive, rare earth elements can be used to prepare fluorescent materials, rare earth metal hydroxide battery, materials, electric light source materials, permanent magnetic materials and catalytic materials. With the increasing use of rare earth elements in various fields, the consumption of rare earth elements is also increasing.
Rare earth is an indispensable strategic resource for the development of high-tech industries and the transformation of traditional industries, and recovering valuable rare earth elements from scrap residue produced from the rare earth molecular sieve production process, spent oil cracking catalyst (spent FCC catalyst), some other rare earth-containing aluminum scrap, and aluminum silicon scrap has good social and economic benefits. At present, the method of recovering rare earth from these rare earth-containing aluminum silicon scrap mainly includes the following steps: Firstly, the rare earth elements and aluminum elements are extracted to the acid leaching solution by acid-leaching with high concentration strong acid, then aluminum elements form sodium metaaluminate and rare earth elements form hydroxide precipitate by extraction-separation or by adding sodium hydroxide into the acid-leaching solution, so as to achieve the purpose of recovery of rare earth. For example, it is reported that after extraction of rare earth and aluminum with acid, the P507 extractant is directly used to separate rare earth, but under the condition of high-concentration of aluminum ion, the separation coefficient of rare earth is low, and the consumption of acid and alkali is high. In the prior art, the rare earth can be directly recovered with a sulfuric acid method, and the recovery efficiency of rare earth can reach more than 75%. However, in this method, aluminum, silicon and rare earth elements were leached simultaneously extracted into the acid leaching solution during acid leaching process and easily leads to the formation of sol system, consumption of a large amount of strong acid for leaching results in increase of recovery costs, and the resulting too high remaining acid and numerous impurity elements in the leaching solution cause difficulty for subsequent separation.
As can be seen, all the current recovery and treatment methods of rare earth-containing aluminum silicon scrap have the defects of high recovery cost and low recovery efficiency. On this basis, it is necessary to find a low cost and high efficiency recovery and treatment method.